The acidosis-induced right shift of the HbO₂ dissociation curve is maintained during erythrocyte storage.

BACKGROUND AND OBJECTIVES

In fresh blood, tissue hypoxia increases microcirculatory acidosis, which enhances erythrocyte O(2) unloading and increases the amount of available O(2). Storage of erythrocytes increases the HbO(2) affinity and reduces O(2) unloading. We examined the development of the affinity change during a period of 5 weeks of storage by present blood bank standards, and investigated to what extent acidosis offsets the affinity change.

MATERIALS AND METHODS

Blood from volunteer donors was processed and stored as erythrocyte concentrates (EC). At 2-5 day intervals, EC were drawn from the bags and suspended in plasma and crystalloids to an Hb ≈ 10 g/dL. The suspensions were adjusted to give a pH of 7.40, 7.10, 6.80 or 6.30 and equilibrated with different gas mixtures to SO(2) 0, 25, 50, 75 and 100%. Measurements of the PO(2)/SO(2) pairs at each pH were used to calculate the position of the HbO(2) curve and its P(50) value.

RESULTS

A significant leftward shift in the HbO(2) curve was established after 1 week of storage; after 2.5 weeks only minor further changes were observed. Acidification right-shifted the HbO(2) curve, after 2.5 weeks of storage the curve at pH 7.10 was similar to that for fresh blood at pH 7.40. Calculations of extractable O(2) showed that the left-shifted HbO(2) curve of stored EC could be advantageous at a low arterial PO(2).

CONCLUSIONS

The rightward shift of the HbO(2) curve due to acidosis is well maintained in stored erythrocytes, a moderate pH decrease offsets the storage-induced increased HbO(2) affinity.